Scientists discover nanoparticles in sunscreen are harmless

Fears about dangers of nanoparticles in sunscreen may be unfounded, with research finding they are unlikely to harm beachgoers.

Scientists have for the first time been able to see how the body's immune system deals with zinc oxide nanoparticles - an ingredient found in many popular sunscreens.

Researchers from the Australian Synchrotron, the Melbourne Centre for Nanofabrication, CSIRO, RMIT and Monash University found while the body absorbed the nanoparticles, it was able to identify and remove the particles before they reached the bloodstream.

''This is the first time that we have shown that the cells of the immune system can break down the nanoparticles directly,'' said Australian Synchrotron and CSIRO bio-inorganic chemist Simon James. ''Previous work was only able to infer that.''

Zinc oxide is added to sunscreen because of its ability to absorb or scatter the sun's ultraviolet radiation and prevent sunburn, but it had not been clear how the body dealt with the nanoparticles that penetrate the skin.

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The researchers used a type of white blood cell called a macrophage which was exposed to zinc oxide nanoparticles. They then counted how many of the tiny cube-shaped particles were absorbed.

Dr James said on average 60,000 tiny nanoparticles made it into a single white blood cell.

''It's a tiny, tiny number, especially seeing as the cells are able to break them down,'' Dr James said.

Within 24-hours, the cells were able to break down 50 per cent to 60 per cent of the nanoparticles, with the majority of the remaining particles in the process of decomposition.

The results published in the journal ACS Nano found the body's immune system did what it should: it broke down nanoparticles before they could enter the bloodstream.

Cancer Council Australia chief executive Ian Olver said the results should reassure those concerned about nanoparticles in sunscreen.

''The nanoparticles in sunscreen are unlikely to cause harm to beachgoers,'' he said.